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Some complex thermal models have also been developed by coupling the heat transfer between grains, workpiece and coolant, whilst the cooling effect of grinding fluids is over simplified assuming the fluids moving as solid body at the wheel surface [4, 5].
A value of 5 microns is used in this paper, corresponding to a relatively sharp status of CBN grains. kg is the thermal conductivity of grits.
Rwch(x) varies with the local undeformed chip thickness, ta(x), which can be evaluated by using the active grit number on the wheel surface.
The evaluated CHTC distributions under creep-feed conditions are believed to be more reliable as the heat partitioning to grinding chips and abrasive grains under these condition were estimated to be less than 10% [12].
At higher material removal rates, i.e., faster worktable speeds, as the mechanism of heat partitioning becomes more complicated, involving much more heat conducted to the grinding chips and abrasives grains, evaluated CHTC distributions may present the variation trend relatively well, as detailed evaluating approach has been carefully used, but perhaps still with some uncertainties. 5.

The applied pressure and the instant contact of the molten metal with the die surface produce a rapid heat transfer condition that yields a pore-free fine-grain casting with mechanical properties approaching those of a wrought product [1].
Sukumaran et al [9] investigated that grain refinement, elimination of casting defects were enhanced by applying pressure during solidification.
The die set was made up of H11 die steel since the die steel has got the ability to withstand high temperatures and high pressures for maximum number of production settings.
It was evident that when the level of squeeze pressure was higher, the hydraulic shock encountered at the molten alloy causes the rapid heat transfer thereby promoting rapid solidification which in turn leads to grain refinement in squeeze cast components to exhibit enhanced mechanical properties. 3.2 Analysis of Micro hardness of the squeeze cast components: Three squeeze cast components of AA6061 were produced by varying the process parameters such as squeeze pressure at three levels (35 MPa, 70 MPa, 105 MPa), die preheat temperature was maintained at 200 °C and pressure applied duration was maintained at 15 seconds respectively.
It was evident that when the level of squeeze pressure was higher, the hydraulic shock encountered at the molten alloy causes the rapid heat transfer thereby promoting rapid solidification which in turn leads to grain refinement in squeeze cast components to exhibit enhanced mechanical properties.

Obviously, the studied flaked particle indicates an inhomogeneous grained surface typical for non-uniform distribution of crystallites.
Thus, the pulverization process has a strong impact on coercivity, which is dependent on a particles/grains size refinement, shape anisotropy, magnetic interactions between the finer particles/nanocrystallites but also on the possible agglomeration of particles for prolonged milling.
The observed changes within magnetic properties can be directly attributed to the refinement of particles/grains size over grinding periods and subsequent increasing within the number of grain boundaries, but also to the change of the anisotropy, to a high non-uniformity of the studied powders which contain not only fine particles but also some agglomerates.

Zr, which is widely said to segregate at the grain boundaries [4] and at the dislocations [5] of nickel aluminides [6], migrates during oxidation towards the oxide/metal interface [7-10].
Zr segregates along the grain boundaries of Al2O3 [11], which reduces the aluminium transport at grain boundaries [10, 12] and, as a consequence, reduces the alumina growth rate [13].
Depths are calculated from the tagging element W of the superalloy [17] Number of 1h-cycles at 1100°C in air Mass Change (mg/cm²) Results Cyclic oxidation.
The next step of this study is to investigate the role of the NiAl grain boundaries in Zr migration.

Ferritic steels are inhomogeneous with respect to the orientation of individual grains.
Also, grain boundaries have properties distinct from those grains.
Both contain carbides or nonmetallic inclusions on the size scale of individuals grains that can act as nucleation sites for cleavage microcracks.
Weibull Stress Model The local approach for cleavage fracture is based on the weakest link concept that postulates that failure of the body of a material containing a large number of statistically independent volumes is triggered by the failure of one of the reference volume [6].

The excellent catalysis molybdenum disulfide, as one typical example of all, has widely mondial application in the area of hydrodesulphurization process of petroleum refining [1,2], due to its quite a number of Mo-S edges, large specific surface area, powerful absorption ability, high activity and other advantages.
Thus the grain diameter got increased.
XRD patterns of the products at different reaction time, (a) 8h, (b) 16h, (c) 24h, (d) 36h As shown in Fig. (8), the grain size of the product gradually becomes larger with reaction time prolonging.
There are some spherical grains of about 1 µm diameter and part fragments in the product of 4h.
This may be attributed to the facts that the impurities adsorbed on the surface of the small grain could reenter the solution and continue to react with H2S gases so as to improve the purity of the precipitate.

Two types of sliding wear behavior were found for magnesium alloys, i.e. mild wear and severe wear as reported by a number of investigations on wear behavior in magnesium alloys [2-8].
The microstructure mainly consists of α-Mg solid solution grains and β-Mg17Al12 phase particles.
After the transition, at 200 N, a DRX region of about 50μm depth without twins appeared beneath worn surface and fine equiaxied recrystallization grains can be observed (Fig. 3(c)).
Only refined α-Mg grains can be observed in the solidified region and most of β-Mg17Al12 phase should have dissolved into α-Mg solid solution matrix.
Meanwhile, the DRX region is composed of fine equiaxed recrystallization α-Mg grains and some particles of β-Mg17Al12 phase.

When the clays are submitted to temperatures above 1000ºC, normally, the final microstructure contains several forms of mullite crystals and quartz grains, which are dispersed in the vitreous matrix.
We analyzed the fracture surface of the samples attacked with HF (40%) in order to observe the morphology of the mullite grains.
For 1200 and 1250°C, it is observed, for both rates, the formation of a silica-rich vitreous phase, evidenced by the appearance of a band in 2θ between 15 and 25º, probably being the result of the decomposition of the cristobalite, which may be related to the large number of fondant oxides in the sample.
According to Magliano and Pandolfelli (2010), the impurities, when in solution in the crystalline structure of mullite, lower the surface energy in some directions of the crystal, leading to a preferential growth in other directions, resulting in the formation of elongated grains.
In (b) we can observe the presence of mullite crystals, presenting acicular characteristics (1) and round grains (3) of various sizes and others with irregular morphology (2), probably due to quartz and cristobalite.

A grain size distribution test of the soil was also performed to show the type and gradation of the soil.
The grain size distribution of the soil, which is used for the unfired soil lime bricks, spans from clay to medium grained sands. 60% of the soil weight consists of fine to medium grained sands.
The number and diameter of the pores at the fiber surface, as shown in Figure 1, contribute to the difference in water content percentages.

Introduction Thermally sprayed coatings, prepared from different classes of materials (metals, ceramics, hardmetals, polymers) have steadily increasing number of applications including electrical insulation, protection against wear and fatigue, as thermal or chemical barrier coatings, or as functional multilayer systems.
The WC grain average size was about 1 µm.
The WC grains appear in lighter grey.
A grey phase appears in large quantities among the WC grains.
As shown in fig. 5, all samples heated in the pendulum are characterized by the presence of a phase rich in cobalt and tungsten surrounding the carbide grains.